I think it’s important to keep in mind that fasting for Catholics doesn’t mean skipping all food that day but rather cutting back. The standard is one regular meal and up to two smaller meals. With that said…
Don’t do anything to endanger your health. It’s true, however, that many of us can cut back a bit on our meals without danger. If you do cut back, test your blood sugar more frequently and deal with any highs of lows as appropriate. It might be wise to consult with your doctor if you have concerns.